1. Field of the Invention
The present invention relates to a reflective liquid-crystal display by means of using a display assembly and a piezoelectric assembly formed under the display assembly. The display assembly is composed of a first transparent nonpiezoelectric-plate having a first transparent electrode under thereof, a second transparent nonpiezoelectric-plate having a second transparent electrode over thereof, and a liquid crystal between the first- and second transparent electrodes. The piezoelectric assembly is composed of a piezoelectric substrate, at least one electrode under the piezoelectric substrate, and a counter electrode over the piezoelectric substrate.
2. Description of the Prior Art
The thin-film transistor (TFT)-type liquid-crystal display is a popular one of conventional liquid-crystal displays, and belongs to nonreflection-type displays. It is good in quality, however has a large problem on electric power consumption, because it needs a backlight. The electric power consumption to the backlight is approximately 80% of all the electric power consumption to the display. In addition, it needs polarizers, so that has a large dimension in thickness. On the other hand, reflection-type displays, for example, polymer dispersed display and guest-host mode display, are superior in electric power consumption to the nonreflection-type displays, however, have a large problem on brightness. In addition, the reflection-type displays have problems on contrast ratio, range of vision, accuracy, clearness, response time, durability, manufacturing, inferiority in liquid crystal, and device size.
An object of the present invention is to provide a reflective liquid-crystal display excellent in brightness and contrast ratio.
Another object of the present invention is to provide a reflective liquid-crystal display operating under low electric power consumption.
Another object of the present invention is to provide a reflective liquid-crystal display with high accuracy and clearness.
Another object of the present invention is to provide a reflective liquid-crystal display operating with a quick response time.
Another object of the present invention is to provide a reflective liquid-crystal display excellent in durability and manufacturing.
Another object of the present invention is to provide a reflective liquid-crystal display without the inferiority in liquid crystal.
Another object of the present invention is to provide a reflective liquid-crystal display without a backlight behind the display.
Another object of the present invention is to provide a reflective liquid-crystal display without polarizers.
Another object of the present invention is to provide a reflective liquid-crystal display excellent in flexibility, that is, capable of, not flat, but curved display.
A still other object of the present invention is to provide a reflective liquid-crystal display having a small size in layer thickness and a simple structure which is very light in weight.
A still further object of the present invention is to provide a reflective liquid-crystal display having a large size in display surface area, that is, excellent in the range of vision.
According to one aspect of the present invention there is provided a reflective liquid-crystal display comprising a display assembly and a piezoelectric assembly, on which the display assembly is formed. The display assembly is composed of first- and second transparent nonpiezoelectric-plates having first- and second transparent electrodes, respectively, and a liquid crystal between thereof. The piezoelectric assembly is composed of a piezoelectric substrate, at least one electrode under the piezoelectric substrate, and a counter electrode over the piezoelectric substrate.
When a first electric signal is applied between the electrode under the piezoelectric substrate and the counter electrode, a thickness-mode vibration is excited in the piezoelectric substrate. The thickness-mode vibration in the piezoelectric substrate causes an elastic wave in the liquid crystal. And then, the elastic wave causes a transition from a transparent- to an opaque state in the liquid crystal.
Under the opaque state in the liquid crystal, if a second electric signal is applied between the first- and second transparent electrodes, electric field is applied to at least a part of the liquid crystal. In this time, the electric field causes a transition from the opaque- to the transparent state only in the part. As a result, a light through the part of the liquid crystal is reflected at the counter electrode, having also a function of an optical mirror.
According to another aspect of the present invention there is provided a reflective liquid-crystal display, wherein the first electric signal has a frequency approximately equal to the resonance frequency of thickness-mode in the combination of the second transparent nonpiezoelectric-plate and the piezoelectric substrate.
According to another aspect of the present invention there is provided a piezoelectric substrate made of a piezoelectric ceramic thin plate, of which the polarization axis is parallel to the thickness direction thereof.
According to another aspect of the present invention there is provided a piezoelectric substrate made of a piezoelectric polymer film.
According to another aspect of the present invention there is provided a reflective liquid-crystal display, wherein the phase velocity of the elastic wave traveling in the second transparent nonpiezoelectric-plate alone is lower than that traveling in the piezoelectric substrate alone, and at the same time, higher than that traveling in the liquid crystal alone.
According to another aspect of the present invention there is provided a reflective liquid-crystal display, wherein the phase velocity of the elastic wave traveling in the first transparent nonpiezoelectric plate alone is higher than that traveling in the liquid crystal alone.
According to another aspect of the present invention there is provided a liquid crystal made of a nematic liquid crystal.
According to another aspect of the present invention there is provided a liquid crystal made of a ferroelectric liquid crystal.
According to another aspect of the present invention there are provided first- and second transparent electrodes made of indium-tin oxide, respectively.
According to another aspect of the present invention there are provided first- and second transparent electrodes comprising a group of slender subelectrodes, respectively. Each of the group forms a stripe pattern, and the stripe direction of the groups are orthogonal from each other. If the second electric signal is applied between at least one of the subelectrodes of the first transparent electrode and that of the second transparent electrode, electric field is applied to at least one crossing zone, in the liquid crystal, between the subelectrodes of the first- and second transparent electrodes. The electric field causes the crossing zone to be in the transparent state.
According to another aspect of the present invention there are provided a first transparent electrode comprising a group of dot-subelectrodes, and a second transparent electrode comprising a plate-shaped electrode. If the second electric signal is applied between at least one of the dot-subelectrodes and the plate-shaped electrode, electric field is applied to at least one zone, in the liquid crystal, between the dot-subelectrode and the plate-shaped electrode. The electric field causes the zone to be in the transparent state.
According to another aspect of the present invention there are provided a first transparent electrode comprising a plate-shaped electrode, and a second transparent electrode comprising a group of dot-subelectrodes. If the second electric signal is applied between the plate-shaped electrode and at least one of the dot-subelectrodes, electric field is applied to at least one zone, in the liquid crystal, between the plate-shaped electrode and the dot-subelectrode. The electric field causes the zone to be in the transparent state.
According to another aspect of the present invention there is provided at least one electrode made of interdigital electrode.
According to another aspect of the present invention there is provided at least one electrode made of interdigital electrode, of which the interdigital periodicity is larger than the thickness of the piezoelectric substrate.
According to another aspect of the present invention there is provided a display assembly further comprising a first transparent polymer-film under the first transparent electrode, and a second transparent polymer-film over the second transparent electrode.
According to another aspect of the present invention there is provided a display assembly further comprising a first transparent polymer film under the first transparent electrode and a second transparent polymer-film over the second transparent electrode. In addition, the liquid crystal is put into a space between the first- and second transparent polymer films with rubbing treatment before the electrode under the piezoelectric substrate and the counter electrode receive the first electric signal.
According to other aspect of the present invention there is provided a display assembly further comprising a metallic thin film as a mirror under the second transparent nonpiezoelectric-plate.
According to a further aspect of the present invention there is provided a display assembly further comprising a color filter. According to another aspect of the present invention there is provided a piezoelectric assembly comprising a piezoelectric substrate, electrodes Ei (i=1, 2, . . . , n) under the piezoelectric substrate, a counter electrode over the piezoelectric substrate, and a switch connected with the electrodes Ei. If the first electric signals are applied between the counter electrode and the electrodes Ei via the switch in turn, thickness-mode vibrations corresponding to the electrodes Ei are excited in the piezoelectric substrate in turn. The thickness-mode vibrations cause elastic waves in the liquid crystal. And then, the elastic waves cause a transition from a transparent- to an opaque state in the liquid crystal.